U.S. patent application number 11/350985 was filed with the patent office on 2006-08-17 for scanning head and printer.
This patent application is currently assigned to Casio Computer Co., Ltd.. Invention is credited to Yasuhiro Daiku, Tetsuya Kusuno, Jun Ogura, Tomoyuki Shirasaki.
Application Number | 20060181603 11/350985 |
Document ID | / |
Family ID | 36815221 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060181603 |
Kind Code |
A1 |
Ogura; Jun ; et al. |
August 17, 2006 |
Scanning head and printer
Abstract
A scanning head includes a surface emitting part array panel
which has an array of surface emitting parts to emit light A
plurality of light guide parts are respectively opposite to the
surface emitting parts. Each of light guide parts has an entrance
plane to receive the light from the surface emitting part, a
reflection plane to reflect the light from the entrance plane, and
an exit plane to emit the light from the reflection plane.
Inventors: |
Ogura; Jun; (Fussa-shi,
JP) ; Daiku; Yasuhiro; (Iruma-shi, JP) ;
Shirasaki; Tomoyuki; (Higashiyamato-shi, JP) ;
Kusuno; Tetsuya; (Iruma-shi, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
220 Fifth Avenue
16TH Floor
NEW YORK
NY
10001-7708
US
|
Assignee: |
Casio Computer Co., Ltd.
Tokyo
JP
|
Family ID: |
36815221 |
Appl. No.: |
11/350985 |
Filed: |
February 9, 2006 |
Current U.S.
Class: |
347/238 |
Current CPC
Class: |
B41J 2/451 20130101 |
Class at
Publication: |
347/238 |
International
Class: |
B41J 2/45 20060101
B41J002/45 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2005 |
JP |
2005-036219 |
Nov 18, 2005 |
JP |
2005-334583 |
Jan 27, 2006 |
JP |
2006-019193 |
Claims
1. A scanning head comprising: a surface emitting part array panel
which has an array of surface emitting parts to emit light; and a
plurality of light guide parts which are respectively opposite to
the surface emitting parts, each of light guide parts having an
entrance plane to receive the light from the surface emitting part,
a reflection plane to reflect the light from the entrance plane,
and an exit plane to emit the light from the reflection plane.
2. The scanning head according to claim 1, wherein each of the
light guide parts has a light adjusting part with the width
gradually increased, as approaching the exit plane.
3. The scanning head according to claim 1, wherein each of the
light guide parts has a light adjusting part with the height
gradually increased, as approaching the exit plane.
4. The scanning head according to claim 1, wherein the light
emission form of each of the surface emitting parts is expanded in
the width, as approaching the exit plane.
5. The scanning head according to claim 1, wherein the reflection
plane defines the whole periphery of the light guide part, with the
entrance plane and exit plane.
6. The scanning head according to claim 1, wherein the exit plane
is has a convex surface.
7. The scanning head according to claim 1, wherein the light guide
part has a hollow body.
8. The scanning head according to claim 1, further comprising a
substrate, wherein each of the surface emitting parts includes an
organic electroluminescent element having a lower electrode, an
organic electroluminescent layer and an upper electrode, and the
entrance plane of each of the light guide parts is opposite to the
upper electrode.
9. The scanning head according to claim 1, wherein the area of the
exit plane is smaller than the area of the entrance plane.
10. A scanning head comprising: a surface emitting part array panel
which has an array of surface emitting parts to emit light; and a
plurality of light guide parts each of which has an entrance plane
opposite to the surface emitting part, a first opposite reflection
plane opposite to the entrance plane in the state inclined to the
entrance plane, a second opposite reflection plane provided along
the first opposite reflection plane and inclined to the entrance
plane to have an included angle larger than an included angle
between the entrance plane and first opposite reflection plane, and
an exit plane to emit the light from the surface emitting part.
11. The scanning head according to claim 10, wherein a reflection
film is formed on the first opposite reflection plane and second
opposite reflection plane of the light guide part.
12. The scanning head according to claim 10, wherein the light
guide part has a first side reflection plane placed between the
entrance plane and first opposite reflection plane, the first side
reflection plane having a height gradually increased, as
approaching the exit plane.
13. The scanning head according to claim 10, wherein the first
opposite reflection plane has a width gradually increased, as
approaching the exit plane.
14. The scanning head according to claim 10, wherein the second
opposite reflection plane has a width gradually increased, as
approaching the exit plane.
15. The scanning head according to claim 10, wherein each of the
light guide parts has a second side reflection plane provided
between the second opposite reflection plane and the surface of the
entrance plane side, the second reflection plane having a height
gradually increased, as approaching the exit plane.
16. The scanning head according to claim 10, wherein each of the
surface emitting parts has an organic electroluminescent element
having a lower electrode, an organic electroluminescent layer and
an upper electrode, and the entrance plane of the light guide part
is opposite to the upper electrode.
17. The scanning head according to claim 10, wherein each of the
light guide parts has a reflection film provided in a part of the
entrance plane opposite to the second opposite reflection
plane.
18. The scanning head according to claim 10, wherein the entrance
plane overlaps a light emission form area of the surface emitting
part.
19. A printer comprising: a surface emitting part array panel which
has an array of surface emitting parts to emit light; and a
plurality of light guide parts each of which is opposite to the
surface emitting part, and has an entrance plane to receive the
light from the surface emitting part, a reflection plane to reflect
the light from the entrance plane, and an exit plane to emit the
light from the reflection plane.
20. The printer according to claim 19, wherein each of the light
guide parts includes a light adjusting part having a width
gradually increased, as approaching the exit plane of the light
guide part.
21. The printer according to claim 19, wherein each of the light
guide parts includes a light adjusting part having a height
gradually increased, as approaching the exit plane of the light
guide part.
22. The printer according to claim 19, wherein the surface emitting
part has a light emission form area expanded in width, as
approaching the exit plane.
23. The printer according to claim 19, wherein the exit plane has a
projected surface.
24. The printer according to claim 19, wherein each of the light
guide parts has a hollow body.
25. The printer according to claim 19, wherein the exit plane has
an area smaller than an area of the entrance plane.
26. A printer comprising: a surface emitting part array panel which
has an array of surface emitting parts to emit light; and a
plurality of light guide parts each of which has an entrance plane
opposite to the surface emitting part, a first opposite reflection
plane opposite to the entrance plane in the state inclined to the
entrance plane, a second opposite reflection plane provided along
the first opposite reflection plane and inclined to the entrance
plane to have an included angle larger than an included angle
between the entrance plane and first opposite reflection plane, and
an exit plane to emit the light from the surface emitting part.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Applications No. 2005-036219,
filed Feb. 14, 2005; No. 2005-334583, filed Nov. 18, 2005; and No.
2006-019193, filed Jan. 27, 2006, the entire contents of all of
which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a scanning head having a
structure suitable for a printer, scanner, copier or other image
input and/or output apparatus, and a printer having such a scanning
head.
[0004] 2. Description of the Related Art
[0005] Page printers have been vigorously developed in recent
years, because they can print on ordinary paper as well as specific
paper. A page printer uses a laser scanning head composed of a
laser diode and a polygon lens. In a laser scanning head, a laser
emitting point is moved by a polygon lens, and printing at
high-speed is difficult.
[0006] For high-speed printing, an LED scanning head using two or
more LEDs has been developed. Two or more LEDs are aligned in an
LED scanning head. These LEDs simultaneously emit light of
different intensity, thereby scanning a photoconductor. As high
picture quality is demanded, very high accuracy is demanded for
packaging of LEDS with high density. This causes a problem of
increased number of components.
[0007] To solve the above problems, Jpn. Pat. Appln. KOKAI
Publication No. 9-226172 proposed a scanning head using an organic
electroluminescent element as an LED.
[0008] However, at present, an organic electroluminescent element
has a problem in luminous intensity and life. Namely, a
light-emitting element requires sufficient amount of light to
expose a photoconductor, and if the luminous intensity per dot of
an organic electroluminescent element is weak, the exposing time
per a dot must be set long. To set the exposing time long, the
printing speed must be delayed. Conversely, if the luminous
intensity per a dot of an organic electroluminescent element is
increased, the exposing time per dot is reduced and the printing
time is reduced, but the life of an organic electroluminescent
element is reduced.
[0009] The luminous flux of an LED such as an organic
electroluminescent element spreads from a light-emitting point, and
it is preferable to provide an optical system between LED and
photoconductor, which gives directivity to incident light from a
dot of an LED to be emitted only to a specified part of a
photoconductor. However, the efficiency of using such an optical
system depends on an angle of taking in light (angular aperture),
and the efficiency of using light is not high in a source like an
LED which causes a light diffusion.
BRIEF SUMMARY OF THE INVENTION
[0010] It is an object of the present invention to provide a
scanning head and a printer, which can efficiently emit light
without increasing the luminous intensity of a surface emitting
part.
[0011] According to a first aspect of the invention, there is
provided a scanning head comprising:
[0012] a surface emitting part array panel which has an array of
surface emitting parts to emit light; and
[0013] a plurality of light guide parts which are respectively
opposite to the surface emitting parts, each of light guide parts
having an entrance plane to receive the light from the surface
emitting part, a reflection plane to reflect the light from the
entrance plane, and an exit plane to emit the light from the
reflection plane.
[0014] According to a second aspect of the invention, there is
provided a printer comprising:
[0015] a surface emitting part array panel which has an array of
surface emitting parts to emit light; and
[0016] a plurality of light guide parts each of which is opposite
to the surface emitting part, and has an entrance plane to receive
the light from the surface emitting part, a reflection plane to
reflect the light from the entrance plane, and an exit plane to
emit the light from the reflection plane.
[0017] In the above scanning head and printer, the light emitted
from the surface emitting part enters the entrance plane of the
light guide part, the entered light is reflected on the reflection
plane, and the reflected light is emitted from the exit plane. As
the exit plane of the light guide part is a plane different from
the entrance plane, and the exit plane is not increased even if the
entrance plane is increased. If the entrance plane is increased and
the light-emitting area of the surface emitting part is increased,
the intensity per unit area of the exit plane is increased without
increasing the light emission intensity per a unit area of the
surface emitting part. Therefore, the exposing time can be reduced.
Further, since the light emission intensity per unit area of the
surface emitting part is not increased, the life of the surface
emitting part can be made long.
[0018] According to a third aspect of the invention, there is
provided a scanning head comprising:
[0019] a surface emitting part array panel which has an array of
surface emitting parts to emit a light beam; and
[0020] a plurality of light guide parts each of which has an
entrance plane opposite to the surface emitting part, a first
opposite reflection plane opposite to the entrance plane in the
state inclined to the entrance plane, a second opposite reflection
plane provided along the first opposite reflection plane and
inclined to the entrance plane to have an included angle larger
than an included angle between the entrance plane and first
opposite reflection plane, and an exit plane to emit the light from
the surface emitting part.
[0021] According to a fourth aspect of the invention, there is
provided a printer comprising:
[0022] a surface emitting part array panel which has an array of
surface emitting parts to emit light; and
[0023] a plurality of light guide parts each of which has an
entrance plane opposite to the surface emitting part, a first
opposite reflection plane opposite to the entrance plane in the
state inclined to the entrance plane, a second opposite reflection
plane provided along the first opposite reflection plane and
inclined to the entrance plane to have an included angle larger
than an included angle between the entrance plane and first
opposite reflection plane, and an exit plane to emit the light from
the surface emitting part.
[0024] In the above scanning head and printer, the light emitted
from the surface emitting part enters the entrance plane of the
light guide part, the entered light is reflected on the first
opposite reflection plane and second opposite reflection plane, and
the reflected light is emitted from the exit plane. The second
opposite reflection plane is provided in the inclined state to have
an included angle larger than the included angle between the first
opposite reflection plane and entrance plane, by transmitting light
in the light guide part, and the directivity of light in the
direction vertical to the exit plane can be improved.
[0025] According to the present invention, the intensity per unit
area of the exit plane can be increased, without increasing the
light emission intensity per unit area of the surface emitting
part. As a result, the life of the surface emitting part can be
made long.
[0026] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0027] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
embodiments given below, serve to explain the principles of the
invention.
[0028] FIG. 1 is a perspective view of an image output
apparatus;
[0029] FIG. 2 is a perspective view showing the configuration of
three dots of a scanning head;
[0030] FIG. 3 is a plane view of the emitting plane of a surface
emitting part array panel for four dots;
[0031] FIG. 4 is an arrow indicated cross section of the plane
taken along lines IV-IV of FIG. 3;
[0032] FIG. 5 is an arrow indicated cross section of the plane
along the cutting lines V-V of FIG. 3;
[0033] FIG. 6A is a plane view showing a dot radiation element in a
modification, and FIG. 6B is a sectional view along the cutting
lines 6B-6B of FIG. 6A;
[0034] FIG. 7A is a plane view showing a dot radiation element in
another modification, and FIG. 7B is a sectional view along the
cutting lines 7B-7B of FIG. 7A;
[0035] FIG. 8A is a plane view showing a dot radiation element in
another modification, and FIG. 8B is a sectional view along the
cutting lines 8B-8B of FIG. 8A;
[0036] FIG. 9 is a perspective view showing the configuration of
three dots of a scanning head in another modification;
[0037] FIG. 10 is a perspective view showing the configuration of
three dots of a scanning head in another modification;
[0038] FIG. 11 is a sectional view of a longitudinal section for
one dot of a scanning head;
[0039] FIG. 12 is a sectional view of a cross section orthogonal to
the cross section of FIG. 11;
[0040] FIG. 13 is a perspective view showing the configuration of
three dots of a scanning head in another modification;
[0041] FIG. 14 is a plane view of the emitting plane of a surface
emitting part array panel in another modification;
[0042] FIG. 15 is an arrow indicated cross section of a plane in
another modification taken along lines XV-XV of FIG. 14;
[0043] FIG. 16 is a perspective view showing the configuration of
three dots of a scanning head in another modification;
[0044] FIGS. 17A and 17B are views for explaining the relation of
an included angle .gamma. between an entrance plane and an opposite
reflection plane, to an emission intensity/luminous intensity,
wherein FIG. 17A shows light guide parts of this invention and
reference example, and FIG. 17B is a graph showing the result of
the relation of an angle .theta. to an emission intensity/luminous
intensity;
[0045] FIGS. 18A to 18C are graphs showing the relation between the
radiation angle and luminous intensity of light emitted from an
exit plane of a light guide part;
[0046] FIG. 19 is a perspective view of an image output apparatus
1;
[0047] FIG. 20 is a perspective view showing the configuration of
three dots of a scanning head;
[0048] FIG. 21 is a plane view of an emitting plane of a surface
emitting part array panel for four dots;
[0049] FIG. 22 is an arrow indicated cross section of the surface
taken along lines XXII-XXII of FIG. 21;
[0050] FIG. 23 is an arrow indicated cross section of the surface
taken along lines XXIII-XXIII of FIG. 21;
[0051] FIG. 24 is a perspective view showing the configuration of
three dots of a scanning head in a comparing example;
[0052] FIG. 25 is a sectional view of a scanning head cut in the
direction of a principal axis;
[0053] FIG. 26 is a perspective view showing the configuration of
three dots of a scanning head;
[0054] FIG. 27 is a plane view of an emitting plane of a surface
emitting part array panel for four dots;
[0055] FIG. 28 is a plane view of an emitting plane of a surface
emitting part array panel for four dots; and
[0056] FIG. 29 is a conceptual illustration of a printer using the
scanning head shown in any one of FIGS. 1 to 28.
DETAILED DESCRIPTION OF THE INVENTION
[0057] Embodiments of the present invention will be explained
hereinafter with reference to the accompanying drawings. In the
embodiments, technically preferably various limitations are given
to embody the invention, but the scope of the invention is not to
be limited to the embodiments and drawings.
[0058] FIG. 1 is a perspective view of an image output apparatus 1.
As shown in FIG. 1, in the image output apparatus 1, a scanning
head 2 is placed with the light-emitting part opposed to a
generating line of a photoconductive drum 3 and the longish side
mode parallel to the rotary shaft of the roller-shaped
photoconductive drum 3. A SELFOC lens array 4 is provided between
the light-emitting part of the scanning head 2 and the generating
line of the photoconductive drum 3. The SELFOC lens array 4 is
composed of a plurality of CELFOC lens arranged in one or more
lines along the light-emitting part of the scanning head 2, each of
which takes a radial straight line of the photoconductive drum 3 as
an optical axis. The CELFOC lens array 4 focuses a light beam from
the light-emitting part of the scanning head 2 on the generating
line of the photoconductive drum 3. The photoconductive drum 3
forms an electrostatic latent image on the peripheral surface when
exposed by the scanning head 2.
[0059] FIG. 2 is a perspective view showing the configuration of
three dots of the scanning head 2. The scanning head 2 has a
surface emitting part array panel 20, and a plurality of light
guide parts 60 arranged in a line on the emission plane 21 of the
surface emitting part array panel 20.
[0060] FIG. 3 is a plane view showing the emission plane 21 (FIG.
4) of the surface emitting part array panel 20. FIG. 4 is an arrow
indicated cross section of the plane along the thickness of an
insulating substrate 30 passing lines IV-IV of FIG. 3. FIG. 5 is an
arrow indicated cross section of the plane along the thickness of
an insulating substrate 30 passing lines V-V of FIG. 3. As shown in
FIG. 3 to FIG. 5, the surface emitting part array panel 20 is
composed of more than one surface emitting part 22 shaped like
substantially a wedge or triangle in a plane view, arranged in a
line on the insulating substrate 30. The light emitted from the
surface emitting part 22 is emitted to the plane (the emission
plane 21) opposite to the insulating substrate 30.
[0061] Each surface emitting part 22 has an organic
electroluminescent element 27. Namely, the surface emitting part 22
has a lower electrode 23 formed on the insulating substrate 30, an
organic electroluminescent layer stacked on the lower electrode 23,
and an upper electrode 26.
[0062] The organic electroluminescent layer has a two-layer
structure consisting of a positive hole carrying layer 24 and a
light-emitting layer 25, for example, as shown in FIG. 4. The
positive hole carrying layer 24 includes polythiophene (PEDOT) as a
conductive high polymer, and polystyrene sulfonic acid (PSS) as
dopant. The light-emitting layer 25 is made of polyfluorene based
light-emitting material, for example. If the surface emitting part
22 emits light as an organic electroluminescent element 27, the
organic electroluminescent layer between the lower electrode 23 and
upper electrode 26 may not have the two-layer structure consisting
of the positive hole carrying layer 24 and light-emitting layer 25.
For example, the layer between the lower electrode 23 and upper
electrode 26 may have a three-layer structure consisting of a
positive hole carrying layer, a light-emitting layer and an
electron carrying layer stacked sequentially on the lower electrode
23, or may have one-layer structure consisting of a light-emitting
layer only, or may have a light-emitting layer and an electron
carrying layer. It may also be a laminated structure having an
electron or positive hole carrying layer interposed between
appropriate layers in these layer structures, or may be another
laminated structure. If the lower electrode 23 is used as a cathode
and the upper electrode 26 is used as an anode, the lower electrode
23 shall have an electric charge carrying layer with an electron
carrying property, and the upper electrode 26 shall have an
electric charge carrying layer with a positive hole carrying
property.
[0063] The lower electrode 23 preferably has a reflective property
for the light of the organic electroluminescent layer, and is
preferably made of material easy to carry a positive hole for the
positive hole carrying layer 24, including metal such as aluminum,
chromium or titanium, when used as an anode. The lower electrode 23
may be a layered product, which has such a reflective conductive
layer as a lower layer, and has a transparent conductive layer
containing at least one of tin doped indium oxide (ITO), zinc doped
indium oxide, indium oxide (In.sub.2O.sub.3), tin oxide
(SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide (CdSnO.sub.4),
as an upper layer just like contacting the positive hole carrying
layer 24.
[0064] The upper electrode 26 has a transmissible property for the
light of the organic electroluminescent layer, and is a layered
product composed of an electron carrying film with a thickness of
1-20 nm, preferably 5-12 nm, which is made of material with a work
function lower than an anode made of a single substance or alloy
containing at least one of indium, magnesium, calcium, lithium,
barium and rare earth metal, and provided on the surface contacting
a charge carrying layer with an electron carrying property, when
used as a cathode; and a transparent conductive layer containing at
least one of tin doped indium oxide (ITO), zinc doped indium oxide,
indium oxide (In.sub.2O.sub.3), tin oxide (SnO.sub.2), zinc oxide
(ZnO) and cadmium tin oxide (CdSnO.sub.4) with a thickness of
30-200 nm, to decrease a sheet resistance as a cathode, when used
as an anode. The upper electrode 26 is composed of a transparent
conductive layer containing at least one of tin doped indium oxide
(ITO), zinc doped indium oxide, indium oxide (In.sub.2O.sub.3), tin
oxide (SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide
(CdSnO.sub.4) on the surface contacting the charge carrying layer
with a positive hole carrying property, when used as an anode
electrode.
[0065] The upper electrode 26 and lower electrode 23 are spaced, so
that at least one of these electrodes is electrically insulated
from the surface emitting part 22 and the two or more surface
emitting parts 22 separately emit light. As shown in FIG. 5, in
this embodiment, the lower electrode 23 is formed separately for
each surface emitting part 22, and the upper electrode 26 is formed
evenly as a film common to all surface emitting parts 22.
[0066] The positive hole carrying layer 24 may be formed separately
for each surface emitting part 22, and may be formed evenly as a
film common to all surface emitting parts 22. The light-emitting
layer 25 may also be formed separately for each surface emitting
part 22, and may be formed evenly as a film common to all surface
emitting parts 22. The positive hole carrying layer 24 may be
formed evenly as a film common to all surface emitting parts 22,
and the light-emitting layer 25 may be formed separately for each
surface emitting part 22, as a light-emitting layer to emit light
with a different color. In this embodiment, the positive hole
carrying layer 24 and light-emitting layer 25 are both formed
separately for each surface emitting part 22.
[0067] In this embodiment, the lower electrode 23, positive hole
carrying layer 24 and light-emitting layer 25 are formed separately
and parted for each surface emitting part 22, and the lower
electrode 23, positive hole carrying layer 24 and light-emitting
layer 25 are enclosed by an insulating film 28. The insulating film
28 is made of inorganic substance such as silicon nitride and
silicon dioxide, or made of photoconductive resin such as
polyimide. The insulating film 28 is preferably lightproof to
prevent propagation of the light emitted from the light-emitting
layer 25 of each surface emitting part 22 to the light-emitting
layer 25 of the adjacent surface emitting part 22.
[0068] The exposed surfaces of the insulating film 28 and upper
electrode 26 (the outside surface of the insulating film 28 and the
upper surfaces of the insulating film 28 and upper electrode 26, as
shown in FIGS. 4 and 5) are covered by a smooth transparent sealing
film 29. As a result, the lower electrode 23, positive hole
carrying layer 24, light-emitting layer 25 and insulating film 28
are sealed by the sealing film 29. As the surface emitting part 22
is a top emission type organic electroluminescent element 27, the
surface (upper surface) of the sealing film 29 becomes an emission
plane of the surface emitting part 22.
[0069] A light guide part 60 is provided oppositely to the surface
emitting part 22. A dot radiation element is composed of the
surface emitting part 22 and the opposite light guide part 60. The
light guide part 60 will be explained hereinafter.
[0070] The light guide part 60 is made of transparent material,
such as polymethyl, methacrylate, polydimethylsiloxane,
polycarbonate, cyclic olefin polymer, and has transmissivity. The
light guide part 60 is a quadrangular pyramid, as shown in FIGS.
1-5.
[0071] One of the four sides of the light guide part 60 (the lower
side in FIGS. 4 and 5) is an entrance plane 63 to receive the light
from the surface emitting part 22, and the bottom (the left side in
FIG. 4) is an exit plane 61. The sides other than the exit plane 61
and entrance plane 63 are reflection planes to reflect the light in
the surface emitting part 22, and composed of an opposite
reflection plane 64 opposite to the entrance plane 63, and side
reflection planes 65 and 66 between the peripheral edge of the
entrance plane 63 and the peripheral edge of the opposite
reflection plane 64. The opposite reflection plane 64 is opposite
to the entrance plane 63 in the state inclined in one direction
toward the entrance plane 63. The exit plane or surface 61 is a
flat plane opposite to the apex angle 62 that is an included angle
between the opposite reflection plane 64 and entrance plane 63. The
included angle formed by the exit plane 61 and entrance plane 63 is
substantially a right angle. The side reflection planes 65 and 66
are rectangular to the entrance plane 63, and the side contacting
the opposite reflection plane 64 is substantially wedge-shaped
having a predetermined elevation angle .theta. (.theta.=0.degree.)
from the apex angle 62 to the exit plane 61. At the same time, the
side reflection planes 65 and 66 are crossed forming an included
angle .gamma. (.gamma.=0.degree.). As a result, the light guide
part 60 is shaped like a pyramid with the rectangular sectional
area cut parallel to the exit plane 61 or the bottom gradually
increased as approaching from the part of the apex angle 62 to the
exit plane 61, or as approaching the exit plane 61. The area of the
entrance plane 63 of the light guide part 60 is set larger than the
area of the exit plane 61.
[0072] On these reflection planes, a reflection film 70 made of
material with high reflectivity to the light from the surface
emitting part 22 (e.g., metal and alloy) is substantially entirely
formed. The reflection film 70 is formed separately for each light
guide part 60. Therefore, the parts covering the opposite
reflection plane 64 and side reflection planes 65 and 66 are
substantially wedge-shaped.
[0073] The exit plane of the surface emitting part 22 is shaped
similar to the entrance plane 63 of the light guide part 60 with
substantially the same dimensions (a little smaller in this
embodiment), as shown in FIG. 3, and emits a light beam like a
wedge expanding in width from one end 31 to the other end 32, or as
approaching the exit plane 61. The area of the exit plane of the
surface emitting part 22 is 80-110%, preferably 85-99% of the area
of the entrance plane 63 of the light guide part 60. For the
emission of sedge-shaped light of the surface emitting part 22, the
electrode formed separately for each surface emitting part 22 out
of the upper and lower electrodes 26 and 23, the lower electrode 23
in this embodiment, is formed like a wedge. In the surface emitting
part 22, the whole exit plane preferably overlaps the entrance
plane 63 of the corresponding light guide part 60, so that light is
not emitted to the light guide part 60 corresponding to the
adjacent surface emitting part 22.
[0074] The entrance plane 63 of the light guide part 60 entirely
contacts just like facing the exit plane of the surface emitting
part 22, the shape of the entrance plane 63 of the light guide part
60 overlaps the emission form of the surface emitting part 22, the
apex angle 62 of the light guide part 60 is located at the vertex
or close to the vertex of one end 31 of the surface emitting part
22, and the entrance plane 61 of the light guide part 60 is
parallel to the bottom side of the other end 32 of the surface
emitting part 22. The direction of a principal axis passing through
one end 31 of the surface emitting part 22 and orthogonal to the
other end face 32 is identical to the direction of a principal axis
Ax (FIG. 4) of the light guide part 60 viewed from the normal of
the surface emitting part 22.
[0075] As explained above, the opposite reflection plane 64 of the
light guide part 60, or the width W (FIG. 3) of the light guide
part 60, is set to be gradually prolonged from the apex 62 to the
exit plane 61, or as approaching the exit plane 61. The side
reflection planes 65 and 66 of the light guide part 60, or the
height H (FIG. 4) of the light guide part 60 are set to be
gradually prolonged from the apex angle 62 to the exit plane 61, or
as approaching the exit plane 61.
[0076] The light guide part 60 can be formed by using nano-inprint
technology, that is, flowing polydimethylsiloxane resin, a kind of
silicon rubber, in a resist pattern, and solidifying it as a
mold.
[0077] As shown in FIG. 1, the exit plane 61 of the light guide
part 60 is opposite to the entrance plane of the SELFOC lens array
4, so that the exit plane 61 of the light guide parts 60 becomes a
light-emitting part of the scanning head 2, and the principal axis
Ax of the light guide part 60 coincides with the optical axis of
the CELFOC lens array 4.
[0078] A driving circuit 80 is provided on one side of the surface
emitting part array panel 20, a wiring 33 connected electrically to
the lower electrode 23 of the surface emitting part 22 is also
electrically connected to the driving circuit 80. The driving
circuit 80 applies a light emission voltage to the lower electrode
23 through the wiring 33. The upper electrode 26 is held at a
constant voltage, and for example, the upper electrode 26 is
grounded.
[0079] For driving the scanning head 2, the driving circuit 80
applies a light emission voltage to the lower electrode 23 of each
surface emitting part 22, based on an image signal. Each surface
emitting part 22 emits a light beam onto the light-emitting layer
25 with the intensity according to the potential difference between
the lower electrode 23 and upper electrode 26. In this time, since
the light-emitting layer overlapping the lower electrode 23 and
upper electrode 26 is wedge-shaped, the surface emitting part 22
emits light like a wedge. The wedge pattern light emitted from the
surface emitting part 22 enters the entrance plane 63 of the light
guide part 60. Since the light guide part 60 is set to have an
included angle .gamma. and elevation angle .theta., the entered
light is given directivity to advance toward the exit plane 61, and
propagated in the light guide part 60, while repeating reflection
on the entrance plane 63, opposite reflection plane 54 and side
reflection planes 65 and 66, and by the reflection member, such as
the lower electrode 23 of the surface emitting part 22, and finally
output from the exit plane 61 of the light guide part 60
substantially along the principal axis Ax of the light guide part
60. In this way, the light guide part 60 itself functions as a
light adjusting part to adjust the directivity of an incident light
beam. Therefore, the light entered the entrance plane 63 of the
light guide part 60 is efficiently emitted from the exit plane 61.
The light beam emitted from the exit plane 61 of the light guide
part 60 is focused at the generating line of the photoconductive
drum 3 by the CELFOC lens array 4, forming an image on the side of
the photoconductive drum 3.
[0080] As explained above, according to this embodiment, since the
area of the exit plane 61 of the light guide part 60 is smaller
than the area of the entrance plane 63, the light emitted from the
surface emitting part 22 into the entrance plane 63 of the light
guide part 60 is outputted from the exit plane 61 in being
converged. As a result, the light beam is emitted with a high
intensity from the exit plane 61 of the light guide part 60, even
if the emission intensity per a unit area of the surface emitting
part 22 is low. Therefore, the photoconductive drum 3 is exposed in
a short time without increasing the sensitivity of the
photoconductive drum, and the photoconductive drum 3 can be rotated
at high speed. As a result, the printing time can be reduced.
[0081] It can be considered to increase the emission intensity of
the surface emitting part 22 to increase the intensity of the light
beam output from the exit plane 61 of the light guide part 60. But,
if the emission intensity of the surface emitting part 22 is
increased, the life of the surface emitting part 22 will be
reduced. However, in this embodiment, the light emitted from the
surface emitting part 22 to the entrance plane 63 of the light
guide part 60 is outputted from the exit plane 61 in the converged
state, and the intensity of the light output from the exit plane 61
of the light guide part 60 can be increased also by increasing the
light-emitting area of the surface emitting part 22. Even if the
light-emitting area of the surface emitting part 22 is increased,
the light intensity on the exit plane 61 of the light guide part 60
is increased without increasing the area of the exit plane 61 of
the light guide part 60, by expanding the area of the entrance
plane 63 of the light guide part 60 to meet the expanded
light-emitting area of the surface emitting part 22. Therefore, an
image can be formed with high resolution without increasing a dot
diameter.
[0082] Further, the shape of the light guide part 60 is set so that
the light entered into the light guide part 60 easily advances to
the exit plane 61 of the light guide part 60, and the light taken
in from the entrance plane of the light guide part 60 can be
efficiently emitted. Directivity is given to increase the light
intensity in the direction of the principal axis Ax of the light
guide part 60, and the light beam can be efficiently applied to the
CELFOC lens array 4. The light use efficiency is increased, and the
photoconductive drum 3 can be exposed in short time and rotated at
high speed without increasing the sensitivity, and the printing
time can be increased.
[0083] The invention is not limited to the above embodiments.
Various improvements and design changes are permitted without
departing from the spirit or essential characteristics of the
invention. Examples of modification will be explained
hereinafter.
[0084] [Modification 1]
[0085] FIG. 6A to FIG. 8B show modifications of the invention, in
which the emission form of the surface emitting part 22 and the
shape of the light guide part 60 are modified. FIG. 6A, FIG. 7A,
and FIG. 8A are plane views showing the emission form of the
surface emitting part 22 together with the light guide part 60.
FIG. 6B, FIG. 7B and FIG. 8B are arrow indicated cross sections of
the planes along the thickness direction of the insulating
substrate 30, passing the cutting lines 6B-6B, 7B-7B and 8B-8B of
FIG. 6A, FIG. 7A and FIG. 8A, respectively. To simplify the
figures, the layers of the surface emitting part 22 are
omitted.
[0086] As shown in FIG. 6A, the included angle at one end 31 is set
to .gamma. (.gamma.>0.degree.), and the surface emitting part 22
is pentagonal with both sides 34 of the other end 32 made parallel
to each other, so that the width is increased to the substantial
halfway and becomes constant from the halfway, as approaching the
exit plane 61. The shape of the entrance plane 63 of the light
guide part 60 is similar to the emission form of the surface
emitting part 22, and the area of the surface emitting part 22 is
80-110%, preferably 85-99% of the area of the entrance plane or
light receiving surface 63 of the light guide part 60. The whole
surface of the surface emitting part 22 preferably overlaps the
entrance plane 63 of the corresponding light guide part 60, so that
light is not emitted into the light guide part 60 corresponding to
the adjacent surface emitting part 22. Similarly, the light guide
part 60 has an included angle of .gamma.. As shown in FIG. 6B, the
opposite reflection plane 64 of the light guide part 60 is divided
into an inclined reflection flat plane 64a which is inclined with a
predetermined elevation angle .theta. from the apex 62 to the exit
plane 61, and a parallel reflection flat plane 64b which
corresponds to the side 34 and is parallel to the entrance plane
63. Therefore, the sectional area parallel to the exit plane 61 is
gradually expanded from the apex angle 62 to both side sides 34,
but the sectional area of the parts corresponding to both sides of
the other end 32 is even. The part surrounded by the inclined
reflection plane 64a, side reflection planes 65/66 and the entrance
plane 63 functions as a light adjusting part to adjust the
directivity of incident light.
[0087] As shown in FIG. 7A, the emission form or plane of the
surface emitting part 22 is trapezoidal with the width increased
from one end 31 to the other end 32, or as approaching the exit
plane 61. The one end 31 is short, and the other end 32 is long. In
the surface emitting part 22, the inclination angle between the
sides is set to .gamma. (.gamma.>0.degree.). In this case, the
shape and dimensions of the entrance plane 63 of the light guide
part 60 is substantially similar to those of the surface emitting
part 22. In the light guide part 60, a flat top plane 64c is formed
at the position opposite to the exit plane 61. One side of the top
64c is identical to one side of the inclined reflection plane 64d
that is opposite to the entrance plane 63 and has the elevation
angle .theta. to the entrance plane 63. The area of the emission
surface of the surface emitting part 22 is 80-110%, preferably
85-99% of the area of the entrance plane 63 of the light guide part
60. The whole surface of the surface emitting part 22 is preferably
overlaps the entrance plane 63 of the corresponding light guide
part 60, so that light is not emitted to the light guide part 60
corresponding to the adjacent surface emitting part 22. In the
surface emitting part 22 having such an emission form, the light
guide part 60 is a quadrangular pyramid, as shown in FIG. 7A and
FIG. 7B. Namely, as the width and height of the light guide part 60
are increased, as approaching the exit plane 61, the area of the
section parallel to the exit plane 61 is expanded from the included
angle between the entrance plane 63 and opposite reflection plane
64, to the exit plane 61. Therefore, the light guide 60 itself
functions as a light adjusting part to adjust the directivity of
incident light.
[0088] In the surface emitting part 22 shown in FIG. 8A, the
emission form of the surface emitting part 22 is hexagonal with the
width increased from one end 31 to the halfway of the other end 32,
that is, to the substantial halfway of the exit plane 61, as
approaching the exit plane 61, and becomes the same thereafter. The
one end 31 has a short width, and the other end 32 is opposite to
the short lateral side and has a long width. In the surface
emitting part 22, the inclination angle between the inclined side
plane portions close to the one end 31 is set to .gamma.
(.gamma.>0.degree.). Both side plane portions 34 adjacent to the
long end 32 are parallel to each other. In this case, also, the
shape of the entrance plane 63 of the light guide part 60 is
substantially similar to the emission pattern of the surface
emitting part 22. The area of the emission plane of the surface
emitting part 22 is 80-110%, preferably 85-99% of the area of the
entrance plane of the light guide part 60. The whole surface of the
surface emitting part 22 preferably overlaps the entrance plane 63
of the corresponding light guide part 60, so that light is not
emitted to the other light guide part 60 corresponding to the
adjacent surface emitting part 22. In the surface emitting part 22
having such an emission form, the oppositing reflection plane 64 of
the light guide part 60 is divided into an inclined reflection
plane or part 64a which is inclined with a predetermined elevation
angle .theta. to the entrance plane 63, a parallel reflection plane
or part 64b which corresponds to the side 34 and is parallel to the
entrance plane 63, and an upper bottom surface or part 64c which is
provided at the position opposite to the exit plane 61, as shown in
FIG. 8B. Namely, though the sectional area parallel to the exit
plane 61 is expanded over the inclined reflection plane 64a, the
sectional area of the parts corresponding to both sides 34 of the
other end 32 is even. As a result, the part surrounded by the
inclined reflection plane 64a, side reflection planes 65, 66 and
entrance plane 63 functions as a light adjusting part to adjust the
directivity of incident light.
[0089] The surface emitting part 22 can be lit in the form shown in
FIG. 8A, by changing appropriately the shape of the light-emitting
layer 24 of the part which overlaps the lower electrode 23 and
upper electrode 26, or the shape of the lower electrode 23 with the
whole surface covered by the upper electrode 26 and light-emitting
layer 25.
[0090] In either FIG. 6A or FIG. 8A, the area of the entrance plane
or light receiving surface 63 of the light guide part 60 is
preferably larger than the area of the exit plane or light emitting
surface 61. Even if the emission intensity per unit area of the
surface emitting part 22 is low, the exit plane 61 of the light
guide part 60 emits a light beam with a high intensity. The light
guide 60 is expanded from the included angle side between the
entrance plane 63 and opposite reflection plane 64, to the exit
plane 61, and the directivity of light in the direction vertical to
the exit plane 61 is improved.
[0091] [Modification 2]
[0092] In the embodiment and modification explained above, the exit
plane 61 of the light guide part 60 is flat. The exit plane 61 may
be configured to function as a lens surface. For example, as shown
in FIG. 9, the exit plane light emitting surface 61 may function as
a condenser lens surface if the surface is formed as a convex
surface. In this case, an the exit plane 61 functions as a lens
surface, and thus emitted light beam can be condensed on the
generating line of the photoconductive drum 3 without the CELFOC
lens array 4 shown in FIG. 1.
[0093] [Modification 3]
[0094] In the embodiment and modifications explained above, the
light guide part is made of transparent solid material such as
resin or glass. A part 167 corresponding to the body of the light
guide part 60 may be hollow, and the hollow light guide part 167
may be made of gaseous matter such as air, as shown in FIG. 10 to
FIG. 12. To form the hollow light guide part 167, a plurality of
hollow light guide parts 167 are depressed or grooved on one side
of an opposite substrate 190 made of such as glass, a reflection
film 168 is formed on the inside wall surface (opposite surface
164) of these hollow light guide parts 167, one hollow light guide
part 167 is related to one surface emitting part 22, and the side
with the hollow light guide part 167 formed is stuck to the
emission plane 21 of the surface emitting part array panel 20. The
hollow light guide part 167 is extended to the side end face of the
opposite substrate 190, and the extended one end of the hollow
light guide part 167 is opened as an opening 161 which becomes an
exit plane or light emitting part. The shape of the hollow light
guide part 167 is preferably the same as the light guide part 60,
and the hollow light guide part 167 is formed as a pyramid with the
opening area reduced in the part from the opening 161 to the end
162. The part 163 of the hollow light guide part 167, facing the
surface emitting part 22 serves as an entrance plane, the opposite
side surface 164 serves as an opposite reflection plane, and the
opening 161 serves as an exit plane. Reflection film 168 are formed
also on the side reflection planes 165 and 166, thus, the side
reflection planes 165 and 166 serve as a reflection plane. Even if
the area of the opening 161 of the hollow light guide part 167 is
smaller than the light emitting area of the surface emitting part
22 and the emission intensity per a unit area of the surface
emitting part 22 is low, as in the case shown in FIG. 10, the
rectangular opening 161 of the hollow light guide part 167 emits
light with a high intensity. The opening area of the hollow light
guide part 167 is reduced in the part from the opening 161 to the
end 162, and the directivity of light is improved.
[0095] [Modification 4]
[0096] In the embodiment and modifications explained above, the
light guide parts 60 and 167 are formed to have wedge-shaped
entrance plane 63 and opposite reflection plane 64, and the area of
the cross section parallel to the exit planes 61 and 161 are
pyramidal expanding in the part from the apex angle 62 (the end
162) to the exit planes 61 and 161. The light guide part 60 may be
formed to have rectangular entrance plane 63 and opposite
reflection plane 64, as shown in FIG. 13. A reflection film is
formed on the surface of its light guide part 60 except the
entrance plane 63 and exit plane 61 facing the surface emitting
part array panel 20. In this case, it is recommendable to make the
emission form or pattern of the surface emitting part 22 the same
as the shape of the entrance panel 63 of the light guide part 60.
Since the light guide part 60 has such a shape that the light in
the light guide part 60 may easily advance to the exit plane 61 of
the light guide part 60, the light taken in from the entrance plane
of the light guide part 60 can be efficiently emit and given
directivity to increase the light intensity in the principal axis
Ax of the light guide part 60.
[0097] [Modification 5]
[0098] In the embodiment and modifications explained above, the
reflection films 70 and 170 are formed separately for the light
guide parts 60 and 167. The reflection films may be one continuous
film covering all light guide parts 60, as shown in FIG. 14 and
FIG. 15. The reflection film 70 is a part hatched by slanted lines
in FIG. 14. The reflection film covers not only the outside surface
of the surface emitting part 22, but also the whole upper surface
of the surface emitting part array panel 20, and prevents leakage
of light from the upper surface of the surface emitting part array
panel 20.
[0099] [Modification 6]
[0100] In the embodiment and modifications explained above, the
scanning head 2 is used as a printer head. The scanning head 2 may
be used as an output head to emit a light beam linearly, by
combining with a linear image pickup element (line sensor) in an
image input apparatus.
[0101] [Modification 7]
[0102] In the embodiment and modifications explained above, the
light guide parts 60 and 167 are formed to have the height
gradually increased based on the elevation angle
.theta.(.theta.>0.degree.) of the opposite reflection planes 64
and 164, as approaching the exit planes 61 and 161. The invention
is not limited to this. Even if the opposite reflection plane 64 is
placed parallel to the entrance plane, directivity is given to
increase the light intensity in the principal axis Ax of the light
guide part 60 as long as the sides 65 and 66 are inclined with an
inclination angle of .gamma. (.gamma.>0.degree.), as shown in
FIG. 16.
[0103] [Modification 8]
[0104] In the embodiment and modifications explained above, the
surface emitting part 22 is composed of the top emission type
organic electroluminescent element 27, which is formed on the side
provided with the light guide part of the insulating substrate 30.
The surface emitting part 22 may be composed of an organic
electroluminescent element of a so-called bottom emission type,
which is formed on the opposite side of the light guide part of the
insulating substrate 30. Namely, an organic electroluminescent
element is provided on one side of the insulating substrate 30, and
the light guide parts 60 and 167 are provided on the opposite side.
In this case, the light from the surface emitting part 22 is
diffused in the insulating substrate 30 according to the thickness
of the insulating substrate 30, before reaching the entrance planes
of the light guide parts 60 and 167. To compensate the
light-diffusion, it is preferable to set the area of the entrance
planes of the light guide parts 60 and 167 sufficiently wide with
respect to the area of the exit plane of the organic
electroluminescence element.
[0105] [Modification 9]
[0106] In the embodiment and modifications explained above, an
organic electroluminescent element is used for the surface emitting
part 22. An inorganic electroluminescent element may be used for
the surface emitting part 22.
EMBODIMENT 1
[0107] The invention will be explained more concretely hereinafter
by taking examples of embodiment.
[0108] In FIG. 17B, X is an example to be compared to X in FIG.
17A, and is a simulation value of the ratio of the emission
intensity (unit: W/sr m.sup.2) of the exit plane 61 of the light
guide part 60 to the emission intensity (unit: W/sr m.sup.2) of the
surface emitting part 22 of the rectangular parallelepiped light
guide part, assuming that the elevation angle .theta. is 0.degree.,
the inclination angle .gamma. is 0.degree. (the opposite reflection
plane 64 is rectangular), the exit plane width W is 10 .mu.m, the
exit plane height H is 10 .mu.m, and the length L from the exit
plane to the opposite side of the light guide part 60 is 200 .mu.m.
Here, the refractive index of the light guide part 60 is 1.0, and
the surface emitting part 22 is set to the same shape and size as
those of the lower side of the light guide part 60.
[0109] In FIG. 17B, Y is an example to be compared to Y in FIG.
17A, and is a simulation value of the ratio of the emission
intensity (unit: W/sr m.sup.2) of the exit plane 61 of the light
guide part 60 to the emission intensity (unit: W/sr m.sup.2) of the
surface emitting part 22 of the rectangular parallelepiped light
guide part, assuming that the elevation angle .theta. is
2.86.degree., the inclination angle .gamma. is 0.degree. (the
opposite reflection plane 64 is rectangular), the exit plane width
W is 10 .mu.m, the exit plane height H is 10 .mu.m, and the length
L from the exit plane to the opposite side of the light guide part
60 is 200 .mu.m. Here, the refractive index of the light guide part
60 is 1.0, and the surface emitting part 22 is set to the same
shape and size as those of the lower side of the light guide part
60.
[0110] In FIG. 17B, Z is an example to be compared to Z in FIG.
17A, and is a simulation value of the ratio of the emission
intensity (unit: W/sr m.sup.2) of the exit plane 61 of the light
guide part 60 to the emission intensity (unit: W/sr m.sup.2) of the
surface emitting part 22 of the rectangular parallelepiped light
guide part, assuming that the elevation angle .theta. is
5.72.degree., the inclination angle .gamma. is 0.degree. (the
opposite reflection plane 64 is rectangular), the exit plane width
W is 10 .mu.m, the exit plane height H is 10 .mu.m, and the length
L from the exit plane to the opposite side of the light guide part
60 is 200 .mu.m. Here, the refractive index of the light guide part
60 is 1.0, and the surface emitting part 22 is set to the same
shape and size as those of the lower side of the light guide part
60.
[0111] As described above, as the elevation angle is increased from
0.degree., the emission intensity per unit area is increased. In
other words, as the elevation angle is increased, the directivity
of the emergent light from the exit plane 61 is improved, and the
intensity of the emergent light is amplified. The emission
efficiency of whole emission energy is 30-50%, and this efficiency
is increased when the angle .theta. is optimized. For example,
assuming that the area of the entrance plane 63 (the light-emitting
area of the surface emitting part 22) is 10 times of the area of
the exit plane 61, when the emission efficiency is 50%, a current
density can be increased to 5 times.
EMBODIMENT 2
[0112] In a rectangular parallelepiped light guide part with an
elevation angle .theta.=0.degree. and an inclination angle
.gamma.=0.degree., the relation between the emission angle and
luminous intensity of the light emitted from the exit plane of the
light guide part is simulated as a comparing example. The exit
plane width W of the light guide part is 10, the exit plane height
H is 10 .mu.m, the length L from the exit plane to the opposite
side is 200 .mu.m, and the refractive index is 1.0. The result is
shown in the pola graph of FIG. 18A. A maximum radiation luminous
intensity is approximately 1740.
[0113] In a light guide part with the same structure as the light
guide part of FIG. 10, the relation between the emission angle and
luminous intensity of the light emitted from the exit plane is
simulated. The width W of the exit plane 161 in FIG. 10 is 10
.mu.m, the exit plane height H is 10 .mu.m, the length L from the
apex angle 162 of the light guide part to the exit plane 161 is 200
.mu.m, and the refractive index of the light guide part 60 is 1.0.
The result is shown in FIG. 18B. In FIGS. 10 to 12, the reflection
planes 165 and 166 are right triangles. In this embodiment, the
side reflection planes corresponding to the reflection planes 165
and 166 are set to an isosceles triangle with the same shape and
size as the opposite reflection plane 164. A maximum radiation
luminous intensity is approximately 3100.
[0114] In another light guide part with the same structure as the
light guide part of FIG. 10, the relation between the emission
angle and luminous intensity of the light emitted from the exit
plane is simulated. The width W of the exit plane 161 in FIG. 10 is
20 .mu.m, the exit plane height H is 20 .mu.m, the length L from
the apex 162 of the light guide part to the exit plane 161 is 200
.mu.m, and the refractive index of the light guide part 60 is 1.0.
The result is shown in FIG. 18C. In FIG. 10, the reflection planes
165 and 166 are right triangles. In this embodiment, the side
reflection planes corresponding to the reflection planes 165 and
166 are set to an isosceles triangle with the same shape and size
as the opposite reflection plane 164. A maximum radiation luminous
intensity is approximately 3690.
[0115] In either FIG. 18A or FIG. 18C, the radius of the graph
indicates a luminous intensity, and the central angle indicates a
radiation angle. As the elevation angle .theta. and inclination
angle .gamma. are increased, a maximum radiation luminous intensity
can be increased.
[0116] Other embodiments to implement the invention will be
explained hereinafter with reference to the figures. These
embodiments are given various technically preferable limitations to
implement the invention, but the scope of the invention is not
limited to these embodiments and illustrated examples.
[0117] FIG. 19 is a perspective view of an image output apparatus
1. As shown in FIG. 19, in the image output apparatus 1, a scanning
head 2 having two or more light-emitting elements is placed with
the light-emitting part opposed to a generating line of a
photoconductive drum 3 and the longish side paralleled to the
rotary shaft of the roller-shaped photoconductive drum 3. A SELFOC
lens array 4 is provided between the light-emitting part of the
scanning head 2 and the generating line of the photoconductive drum
3, with two or more CELFOC lenses arranged in a line or two or more
lines along the light-emitting part of the scanning head 2, each of
which takes a radial straight line of the photoconductive drum 3 as
an optical axis. The light beam from the light-emitting part of the
scanning head 2 is focused onto the generating line of the
photoconductive drum 3 by the CELFOC lens.
[0118] FIG. 20 is a perspective view showing the configuration of
three dots of the scanning head 2. The scanning head 2 has a
surface emitting part array panel 20, and a plurality of light
guide parts 60 aligned arranged on the emission plane 21 of the
surface emitting part array panel 20.
[0119] FIG. 21 is a plane view of the emission plane 21 of the
surface emitting part array panel 20. FIG. 22 is an arrow indicated
cross section of the plane along the thickness of an insulating
substrate 30, passing lines XXII-XXII of FIG. 21. FIG. 23 is an
arrow indicated cross section of the plane along the thickness of
an insulating substrate 30, passing lines XXIII-XXIII of FIG.
21.
[0120] As shown in FIGS. 21 to 23, the surface emitting part array
panel 20 is composed of an insulating substrate 30 and a plurality
of surface emitting parts 22 shaped like substantially a rectangle
(quadrilateral) in a plane view, and aligned on the insulating
substrate 30 to be placed underside of the light guide part 60.
[0121] Each of the surface emitting parts 22 has an organic
electroluminescent element 27. Namely, the surface emitting part 22
has a light reflective lower electrode 23 formed on the insulating
substrate 30, an organic EL layer stacked on the lower electrode
23, and a transparent upper electrode 26.
[0122] The organic electroluminescent layer has a positive hole
carrying layer 24 and a light-emitting layer 25, for example, as
shown in FIG. 22. The positive hole carrying layer 24 contains
polythiophene (PEDOT) as a conductive high polymer, and polystyrene
sulfonic acid (PSS) as dopants. The light-emitting layer 25
contains a conjugated double-bond polymer such as polyphenylene
vinylene, for example. If the surface emitting part 22 emits light
as an organic electroluminescent element 27, the organic
electroluminescent layer between the lower electrode 23 and upper
electrode 26 may not have the two-layer structure consisting of the
positive hole carrying layer 24 and light-emitting layer 25. For
example, the layer between the lower electrode 23 and upper
electrode 26 may have a three-layer structure consisting of a
positive hole carrying layer, a light-emitting layer and an
electron carrying layer stacked sequentially on the lower electrode
23, or may have one-layer structure consisting of a light-emitting
layer only, or may have a light-emitting layer and an electron
carrying layer. It may also be a laminated structure having an
electron or positive hole carrying layer interposed between
appropriate layers in these layer structures, or may be another
laminated structure. If the lower electrode 23 is used as a cathode
and the upper electrode 26 is used as an anode, the lower electrode
23 shall have an electric charge carrying layer with an electron
carrying property, and the upper electrode 26 shall have an
electric charge carrying layer with a positive hole carrying
property.
[0123] The lower electrode 23 preferably has a reflective property
for the light of the organic electroluminescent layer, and is
preferably made of material easy to carry positive holes for the
positive hole carrying layer 24, containing metal such as aluminum,
chromium or titanium, when used as an anode. The lower electrode 23
may be a layered product, which has such a reflective conductive
layer as a lower layer, and has a transparent conductive layer
containing at least one of tin doped indium oxide (ITO), zinc doped
indium oxide, indium oxide (In.sub.2O.sub.3), tin oxide
(SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide (CdSnO.sub.4),
as an upper layer just like contacting the positive hole carrying
layer 24.
[0124] The upper electrode 26 has a transmissible property for the
light of the organic electroluminescent layer, and has an electron
carrying film with a thickness of 1 to 20, preferably 5 to 12 nm,
which is made of material with a work function lower than an anode
made of a single substance or alloy containing at least one of
indium, magnesium, calcium, lithium, barium and rare earth metal,
and provided on the surface contacting a charge-carrying layer with
an electron-carrying property, when used as a cathode; and a
transparent conductive layer to decrease a sheet resistance as a
cathode. The transparent conductive layer is a layered product,
which contains at least one of tin doped indium oxide (ITO), zinc
doped indium oxide, indium oxide (In.sub.2O.sub.3), tin oxide
(SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide (CdSnO.sub.4).
When used as an anode electrode, the upper electrode 26 contains at
least one of tin doped indium oxide (ITO), zinc doped indium oxide,
indium oxide (In.sub.2O.sub.3), tin oxide (SnO.sub.2), zinc oxide
(ZnO) and cadmium tin oxide (CdSnO.sub.4), on the surface
contacting a charge carrying layer with a positive hole carrying
property, and has the thickness of preferably 30 to 200 nm.
[0125] Like the organic electroluminescent element 27 emits light
independently at an appropriate timing, in the surface emitting
part 22, at least one of the upper electrode 26 and lower electrode
23 is separately formed to be electrically insulated for each
organic electroluminescent element 27. In this embodiment, the
lower electrode is formed separately for each surface emitting part
22, and the upper electrode 26 is formed as a film evenly on the
plane common to all surface emitting parts 22.
[0126] The positive pole carrying layer 24 may be separately formed
for each surface emitting part 22, or may be formed as a film
evenly on the plane common to every surface emitting part 22. It is
also permitted to form the positive pole carrying layer 24 as a
film on the plane common to all surface emitting parts 22, and form
the light-emitting layer separately as a light-emitting layer to
emit light of different color for each surface emitting part 22. In
this embodiment, both positive hole carrying layer 24 and
light-emitting layer 25 are separately formed for each surface
emitting part 22.
[0127] In this embodiment, the lower electrode 23, positive hole
carrying layer 24 and light-emitting layer 25 are separately formed
for each surface emitting part 22. The lower electrode 23, positive
hole carrying layer 24 and light-emitting layer 25 are parted by
the insulating film 28 for each surface emitting part 22, and
enclosed by the insulating film 28 in a plane view. The insulating
film 28 is made of inorganic material such as silicon nitride and
silicon dioxide, or photoconductive resin such as polyimide. The
surface emitting part 22 emits light into the light-emitting layer
25. The surface of the insulating film 28 is preferably lightproof
to prevent propagation of the light emitted in the light-emitting
layer 25 of a certain surface emitting part 22 to the
light-emitting layer 25 of the adjacent surface emitting part
22.
[0128] The insulating film 28 and upper electrode 26 are covered
with a transparent sealing film 29 having a smooth surface. The
lower electrode 23, positive hole carrying layer 24, light-emitting
layer 25 and insulating film 28 are entirely sealed with the
sealing film 29. Since the surface emitting part 22 is a top
emission organic electroluminescent element, the surface of the
sealing film 29 becomes an exit plane of the surface emitting part
22.
[0129] One light guide part 60 is opposite to one surface emitting
part 22, and a dot radiation element is composed of one surface
emitting part 22 and one opposite light guide part 60.
[0130] The light guide part 60 will be explained hereinafter. As
shown in FIG. 19 to FIG. 23, the light guide part 60 is placed at
the position corresponding to the surface emitting part 22, and
enclosed by the sealing film 29 and a cylindrical light-reflecting
part 140 having an opened entrance plane 63 to receive the light
from the surface emitting part 22. The light-reflecting part 140
has a first reflecting part 160 which faces the surface emitting
part 22 and has a light-reflective inside surface, a second
reflecting part 150 which is connected to the first reflecting part
160 on the boundary plane 68 that becomes a light-emitting end face
in the first reflecting part 160, and has a light-reflective inside
surface, and a third reflecting part 170 which is placed under the
second reflecting part 150, and has a light-reflective front
surface. The first reflecting part 160 and second reflecting part
150 are formed by a continued reflection film 70. The third
reflecting part 170 is separately formed by a reflection film 71.
The reflection films 70 and 71 are both made of light-reflective
metal or alloy, and preferably have a high reflectivity for the
light from the organic electroluminescent element 27. There
reflection films are preferably made of silver or aluminum if the
main light-emitting wavelength range of the organic
electroluminescent element 27 is over 400 nm, and gold if the
wavelength range is over 600 nm.
[0131] The first reflecting part 160 is opened in the entrance
plane 63 on the lower side corresponding to the surface emitting
part 22 and boundary plane or the front side 68. The second
reflecting part 150 is opened in the boundary plane 68, the exit
plane or the front side 52 that becomes a light-emitting end face
opposite to the boundary plane 68, and the lower side of the
surface emitting part 22. The exit plane 52 is positioned on the
same plane as the end face 30a of the insulating substrate 30. The
third reflecting part 170 is formed like a plane and placed under
the opened lower side of the second reflecting part 150.
[0132] The first side reflection planes 65 and 66 arranged parallel
in the first reflecting part 160 are triangles with the height
decreased from the front to the rear, and the space enclosed by the
first reflecting part 160 and the sealing film 29 forms a
triangular prism. In the second reflecting part 150 and third
reflecting part 170, the boundary plane 68 and the exit plane 52
faced and opened are similar quadrilaterals of different sizes, and
the space enclosed by the second reflecting part 150 and third
reflecting part 170 forms a square pyramid.
[0133] The light guide part 60 is provided with the entrance plane
63, the exit plane 52, the first opposite reflection plane 64
opposite to the entrance plane 63, the first side reflection planes
65 and 66 between the peripheral edges of the entrance plane 63 and
first opposite reflection plane 64, the second reflection plane 53
on the plane (the top of the sealing film 29) of the extension to
the front of the entrance plane 63, and the first opposite
reflection plane 64. The light guide part 60 has also a second
opposite reflection plane 54 continuing to the first opposite
reflection plane 64, opposite to the second reflection plane 53 in
the state inclined to the second reflection plane 53, and second
side reflection planes 55 and 56 between the peripheral edges of
the second reflection plane 53 and second opposite reflection plane
54.
[0134] The reflection film 70 in the first reflecting part 160
contacts the light-reflective first opposite reflection plane 64,
and the light-reflective first side reflection planes 65 and 66
between the peripheral edges of the entrance plane 63 and first
opposite reflection plane 64.
[0135] The reflection film 71 of the third reflecting part 170
formed on the front portion of the sealing film 29 contacts the
second reflection plane 53 having the light-reflective surface.
[0136] The reflection film 70 of the second reflecting part 150 is
opposite to the second reflection plane 53 of the third reflecting
part 170, and provided continuously along the first opposite
reflection plane 64, and adjacent to the light-reflecting second
opposite reflection plane 54 and the second side reflection planes
55 and 56 between the peripheral edges of the second reflection
plane 53 and second opposite reflection plane 54, in the state
inclined to the second reflection plane 53.
[0137] The light emitted from the surface emitting part 22 into the
light guide part 60 in the light reflecting part 140 is set to be
reflected in the light reflecting part 140 and then outputted from
the exit plane 52, or outputted directly from the exit plane
52.
[0138] The lower electrode 23 has also a function as a reflection
plane to reflect the light entered directly and the light reflected
on the first opposite reflection plane 64 and first side reflection
planes 65 and 66, among the light emitted from the light-emitting
layer 25.
[0139] The above mentioned entrance plane 63 is relatively inclined
to the first opposite reflection plane 64. The entrance plane 63 is
set substantially rectangular to the boundary plane 68 between the
first reflecting part 160 and second reflecting part 150 (the
surface opposite to the included angle between the entrance plane
63 and first opposite reflection plane 64). The first side
reflection planes 65 and 66 are originally rectangular to the
entrance plane 63, and the side contacting the first opposite
reflection plane 64 is substantially wedge-shaped with a fixed
elevation angle .theta. (.theta.>0.degree.) from the end portion
62 to the boundary plane. Therefore, the sectional area of plane
cut parallel to the boundary plane 68 is gradually increased from
the end portion 62 to the boundary plane 68, or as approaching the
boundary plane 68.
[0140] In the entrance plane 63 and first opposite reflection plane
64, the width W of the light guide part 60 is substantially equal
from the end portion 62 to the boundary plane 68. The entrance
plane 63 and first opposite reflection plane 64 are rectangles
(quadrilaterals) becoming long from the end portion 62 to the
boundary plane 68. The area of the entrance plane 63 is larger than
the area of the boundary plane 68. For example, the entrance plane
63 is a rectangle of 300 .mu.m.times.10 .mu.m, and the area is 3000
.mu.m.sup.2. The boundary plane 68 is a rectangle of 10
.mu.m.times.5 .mu.m, and the area is 50 .mu.m.sup.2.
[0141] In the first side reflection planes 65 and 66, the height H
of the light guide part 60 is gradually increased in the part from
the end portion 62 to the boundary plane 68, or as approaching the
boundary plane 68.
[0142] The exit plane 52 and second reflection plane 53 are both
inclined to the second opposite reflection plane 54. The exit plane
52 is a plane opposite to the end portion 62, or the included angle
portion between the first opposite reflection plane 64 and entrance
plane 63. In the exit plane 52, the included angle to the second
reflection plane 53 is substantially a right angle.
[0143] The second side reflection planes 55 and 56 are both
orthogonal to the second reflection plane 53, and the side
contacting the second opposite reflection plane 54 is substantially
wedge-shaped with a fixed second elevation angle .theta.'
(.theta.'>.theta.), from the boundary plane to the exit plane
52, and the sectional area of the plane cut parallel to the exit
plane 52 is gradually increased from the boundary plane 68 to the
exit plane 52, or as approaching the exit plane 52. The area of the
entrance plane 63 is larger than the area of the exit plane 52.
Concretely, the exit plane 52 is a rectangle of 20 .mu.m.times.10
.mu.m, and its area is 200 .mu.m.sup.2.
[0144] The second elevation angle .theta.' is larger than the first
elevation angle .theta., and the first opposite reflection plane 64
and second opposite reflection plane 54 are formed to be a valley
in the boundary plane 68.
[0145] The width W of the second reflection plane 53 and second
opposite reflection plane 54 is gradually increased from the
boundary plane 68 to the exit plane 52. The height H of the second
side reflection planes 55 and 56 is gradually increased from the
boundary plane 68 to the exit plane 52.
[0146] The reflection film 70 is preferably continued to the first
reflecting part 160 and second reflecting part 150, but may be
separated in the boundary plane 68. The shape of the first opposite
reflection plane 64 and the shape of the reflection film 70 in the
first reflecting part 160 contacting the first reflection plane 64
are substantially rectangular in a plane view, as shown in FIG. 21.
The shapes of the first side reflection planes 65 and 66 and the
shape of the reflection film 70 in the first reflecting part 160
contacting the first side reflection planes 65 and 66 are
triangular, as shown in FIG. 22. The shape of the second opposite
reflection plane 54 and the shape of the reflection film 70 in the
second reflecting part 150 contacting the second opposite
reflection plane 54 are trapezoidal, as shown in FIG. 21. The
shapes of the second side reflection planes 55 and 56 and the shape
of the reflection film 70 in the second reflecting part 150
contacting the second side reflections planes 55 and 56 are
trapezoidal, as shown in FIG. 22. The shape of the second
reflection plane 53 and the shape of the reflection film 71 in the
third reflection part 170 contacting the second reflection plane 53
are trapezoidal.
[0147] The exit plane of the surface emitting part 22 is shaped
similar to the entrance plane 63 with substantially the same
dimensions as shown in FIG. 21, and emits a light beam like a
rectangle cross section that becomes long from one end 31 to the
other end 32. The area of the exit plane of the surface emitting
part 22 is 80-110%, preferably 85-99% of the area of the entrance
plane 63 of the light guide part 60. For the emission of
rectangular light beam of the surface emitting part 22, one of the
upper and lower electrodes 26 and 23 formed electrically
independent of each surface emitting part 22, i.e. the lower
electrode 23 in this embodiment is rectangular. In the surface
emitting part 22, the whole plane preferably overlaps only the
corresponding entrance plane 63 to prevent emission of light to the
light guide part 60 corresponding to the adjacent surface emitting
part 22.
[0148] The entrance plane 63 contacts just like facing the exit
plane of the surface emitting part 22, the entrance plane 63
overlaps the emission form area of the surface emitting part 22,
the end portion 62 is placed close to the peripheral edge of one
end 31 of the surface emitting part 22, and the boundary plane 68
is parallel to the bottom side of the other end 32 of the surface
emitting part 22. The principal axis direction from one end 31 of
the surface emitting plane 22 to the other end 32 is identical to
the direction of the principal axis Ax of the light guide part 60
viewed from the normal of the surface emitting part 22, as shown in
FIG. 21.
[0149] The reflection film 70 of the light reflecting part 140
defining the shape of the light guide part 60 can be molded
three-dimensionally by pouring reflective material that becomes a
reflective film 70, into a three-dimensional mold controlled in
depth by changing the acceleration voltage, when exposing an
electro beam.
[0150] As shown in FIG. 19, the exit plane 52 of the light guide
part 60 is opposite to the entrance plane of the SELFOC lens array
4, so that the exit plane 52 of each light guide part 60 becomes a
light-emitting part of the scanning head 2, and the principal axis
Ax of the light guide part 60 coincides with the optical axis of
the CELFOC lens array 4.
[0151] A driving circuit 80 is provided on one side of the surface
emitting part array panel 20, a wiring 33 of the surface emitting
part 22 is connected to the driving circuit 80. The driving circuit
80 applies desired voltage or current to the organic
electroluminescent element 27 through the wiring 33, based on the
image signal that becomes a printing data, and causes the organic
electroluminescent element 27 to emit light appropriately.
[0152] As the shape of the light-emitting layer 25 of the part
overlapping the lower electrode 23 and upper electrode 26 is
rectangular, the surface emitting part 22 emits a light beam like a
rectangle. The light emitted from the surface emitting part 22
enters the entrance plane 63 of the light guide part 60. The
entered light is propagated in the first reflecting part 160 while
repeating reflection on the entrance plane 63, first opposite
reflection plane 64 and first side reflection planes 65, 66,
according to the first elevation angle .theta.. The light is
further reflected on the second reflection plane 53, second
opposite reflection plane 54 and second side reflection planes 55,
56, according to the second elevation angle .theta.', and while
repeating reflection, the light is given directivity to advance to
the exit plane 52, and propagated in the light guide part 60, and
output from the exit plane 52 of the light guide 60 substantially
along the principal axis Ax of the light guide part 60. In this
way, the light guide part 60 itself functions as a light adjusting
part to adjust the directivity of incident light. Therefore, the
light entering the entrance plane 63 of the light guide part 60 is
efficiently emitted from the exit plane 52, and the directivity in
the vertical direction to the exit plane 52 is improved. The light
beam emitted from the exit plane 52 is focused on the generating
line of the photoconductive drum 3 rotated by the CELFOC lens array
4, and an image is formed on the side of the photoconductive drum
3.
EMBODIMENT 3
[0153] The amount of light from an exit plane of a triangular prism
shape light guide part with a triangular side defined only by the
first reflecting part 160 is compared with that of the light guide
part 60 (an example of the present invention) defined by the first
reflecting part 160, second reflecting part 150 and third
reflecting part 170 (a comparing example), as shown in FIG. 24. The
surface emitting part 22 is set to the same or similar shape and
size in either the comparing example or the example of the present
invention, and the first reflecting part 160 is also set to the
same or similar shape and size in either the comparing example or
the example of the present invention. But, in the comparing
example, the boundary plane 68 that is the light-emitting end face
of the first reflecting part 160 is set to the substantially same
level as the end face 30a of the insulating substrate.
[0154] The light guide part 60 in the first reflecting part 160 is
set to 300 .mu.m in length, 10 .mu.m in width, and 5 .mu.m in
height on the boundary plane 68. The light guide part 60 in the
second reflecting part 150 and third reflecting part 170 is set to
40 .mu.m in length, 10 .mu.m in width on the boundary plane 68, 20
.mu.m in width on the exit plane 52, 5 .mu.m in height on the
boundary plane 68, and 10 .mu.m in height on the exit plane 52.
[0155] Difference in the amount of light emitted within an angle of
25.degree. to the principal axis Ax of the light guide part 60 is
compared in a relative value, assuming that the first reflecting
part 160 and second reflecting part 150 are filled with air
(refractivity 1.00), and the emission flux density per area of 1
.mu.m.sup.2 of the surface emitting part 22 is "1".
[0156] In the light emitted from the exit plane, the amount of
light emitted within an angle of 25.degree. to the principal axis
Ax is "131" in the comparing example, and "420" in the example of
the invention. Therefore, the amount of light emitted within an
angle of 25.degree. can be increased to approximately 3.2 times of
a conventional value.
[0157] According to the embodiment of the invention, the light
emitted from the surface emitting part 22 enters the entrance plane
63 of the light guide part 60, advances in the light guide part 60
along its longitudinal direction or an axis Ax, and goes out from
the exit plane 52. The second opposite reflection plane 54 is
provided in the state inclined to the second reflection plane 53 to
have a second included angle .theta.' larger than the first
included angle .theta. between the first opposite reflection plane
64 and entrance plane 63. This can improve the directivity of light
in the vertical direction to the exit plane 52, and increase the
amount of emitted light without reducing the life of the element.
As a result, a crosstalk between adjacent pixels can be
prevented.
[0158] Since the area of the exit plane 52 is smaller than the area
of the entrance plane 63, the light applied from the surface
emitting part 22 to the entrance plane 63 is output from the exit
plane 52 in the converged state. Thus, even if the emission
intensity per unit area of the surface emitting part 22 is low,
light is output from the exit plane 52 with high intensity.
Therefore, the photoconductive drum 3 is exposed in a short
exposing time, and can be rotated at high speed, so that the
printing time can be reduced.
[0159] It can be considered to increase the emission intensity of
the surface emitting part 22 in order to increase the intensity of
the light emitted from the exit plane 52. But, the increased
emission intensity of the surface emitting part 22 will reduce the
life of the surface emitting part 22. Since the light applied from
the surface emitting part 22 to the entrance plane 63 is output
from the exit plane 52 in the converged state, it is also possible
to increase the intensity of the light from the exit plane 52 by
increasing the light-emitting area of the surface emitting part 22.
If the light-emitting area of the surface emitting part 22 is
increased, the light intensity on the exit plane 52 is increased by
increasing the area of the entrance plane 63 to meet the increased
light-emitting area, without increasing the area of the exit plane
52. Therefore, an image can be formed with high resolution without
increasing the diameter of a dot.
[0160] Since the shape of the light guide part 60 is set so that
the light applied into the light guide part 60 can easily advance
to the exit plane 52, the light beam taken in from the entrance
plane 63 can be efficiently emitted. Further, since directivity is
given to increase the light intensity in the principal axis Ax of
the light guide part 60, light can be efficiently applied to the
CELFOCS lens array 4, and the light use efficiency is increased.
Therefore, the photoconductive drum 3 is exposed in a short
exposing time, and can be rotated at high speed. As a result, the
printing time can be reduced.
[0161] The present invention is not limited to the embodiment
described above. The invention may be modified and changed in
design without departing from its spirit or essential
characteristics.
[0162] For example, the light guide part 60 parted by the
reflection films 70 and 71 is filled with gaseous matter having
transmissivity such as air. The light guide part is not limited to
this. It may be made of transparent solid material with a low
refractivity, for example, fluorine based resin composed of
polymers such as polydimethylsiloxane resin, ethylene fluoride and
propylene fluoride, epoxy based thermosetting resin and glass, or
transparent liquid material with a low refractivity, for example,
water (refractivity n.sub.D.sup.20=1.33), methyl alcohol
(refractivity n.sub.D.sup.20=1.32), or ethyl alcohol (refractivity
n.sub.D.sup.20=1.36). In case of using liquid material, it is
necessary to seal the liquid body sufficiently with another
transparent member, to prevent leakage from the exit plane 52. In
the case of using solid material, the light guide part may be
formed by flowing solution of solid material into a mold of resist
pattern processed minutely to a nano-size and solidifying it, by
using nano-inprint technology. The refractivity is preferably as
close to 1 of air as possible, and preferably 1.5 or less as a
resin. A reflection plane may be formed by forming a reflective
film at a specified portion of a light guide part.
[0163] In the above embodiment, the second reflecting part 150 may
be formed, for example, as shown in FIG. 25, by forming the surface
emitting part 22 on the insulating substrate 30 up to the lower
side of the second reflecting part 150, without providing the
reflection film 71, and making the light-reflecting lower electrode
23 of the organic electroluminescent element 27 as a third
reflecting part 170.
[0164] In the above embodiment, the surface emitting part 22 (the
light-emitting layer 25 of the part overlapping the lower electrode
23 and upper electrode 26), the entrance plane 63 and first
opposite reflection plane 64 of the light guide part 60, and the
first reflecting part 160 contacting the first opposite reflection
plane 64 are rectangular, but they may be shaped as a triangle as
shown in FIGS. 26 and 27. Namely, the light guide part 60 in the
first reflecting part 160 may be formed as a square pyramid having
the boundary plane 68 as a bottom in order to increase the emission
efficiency. Even in this case, .theta.'>.theta.. The angle
.alpha. of the end portion 162 in the first reflecting part 160 and
angle .alpha.' corresponding to the second opposite reflection
plane 54 in the second reflecting part 150 are set to
.alpha.<.alpha.'. These shapes may be realized by forming an
insulating film to cover the peripheral edge of the lower electrode
23 and forming a triangular opening to expose the lower electrode
23 in the insulating film.
[0165] The surface emitting part 22 (the light-emitting layer 25 of
the part overlapping the lower electrode 23 and upper electrode
26), the entrance plane 63 and first opposite reflection plane 64
of the light guide part 60, and the first reflecting part 160
contacting the first opposite reflection plane 64 may be
trapezoidal as shown in FIG. 28. Even in this case,
.theta.'>.theta.. The angle .beta. of the end portion 262 in the
first reflecting part 160 and angle .beta.' corresponding to the
second opposite reflection plane 54 in the second reflecting part
150 are set to .beta.<.beta.'. These shapes may be realized by
forming an insulating film to cover the peripheral edge of the
lower electrode 23 and forming a triangular opening to expose the
lower electrode 23 in the insulating film.
[0166] If consistency is ensured, the configurations of these
modifications may be appropriately combined.
[0167] The image output apparatus 1 of the embodiments described
above can be applied to a printer used in a copier. As shown in
FIG. 29, in addition to the scanning head 2, photoconductive drum 3
and CELFOCS lens array 4 of the image output apparatus 1, an
electrophotographic printer 301 has a paper feed cassette 201
containing paper sheets 205 as a printing recording medium, a paper
feed roller 202 to feed the paper sheets 205 one by one from the
paper feed cassette 201, a developer 208 to develop an
electrostatic latent image formed on the peripheral surface of the
photoconductive drum 3 to a toner image, a pair of standby rollers
203 to adjust the timing of feeding the paper sheets 205 to a toner
image formed on the photoconductive drum 3, a transfer unit 206 to
transfer a toner image to a paper sheet, a fixing roller 204 to
thermally fix the toner image transferred from the photoconductive
drum 3 to a paper sheet in the transfer unit 206 to a paper sheet,
and a cleaner 207 to remove toner remained on the photoconductive
drum 3.
[0168] An image data stored in a frame memory is converted to an
analog signal of corresponding tone by a digital to analog
converter, and amplified to a fixed potential by an operational
amplifier, and sent to a shift register in the driving circuit 80.
In the driving circuit 80, the image data is sequentially
transferred in the shift register, interlocking with the output of
a clock signal. When image data for one line is stored in the
analog shift register, the data is transferred to a latch circuit.
The data transferred to the latch circuit is taken in an emission
luminance control circuit based on a synchronizing signal with
fixed timing, and modulated to current data or voltage data to
cause the organic electroluminescent element 27 to emit light with
the luminance corresponding to the data, and output to the organic
electroluminescent element 27.
[0169] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *